The present invention relates to memory media and input/output device packages. Typically, the package holds a printed circuit board, where the device conforms to the standards set by PCMCIA, JEDIC, ISO, and etc. for peripheral devices.
The current trend in the computing hardware, telecommunications and electronics industries is to miniaturize components and devices and to place as many of the components and devices next to each other so as to provide quality technical performance in a small package. Such packages have typically been formed from steel with plastic molded frames. Such packages do not provide a rigid, robust, and precise datum surface upon which a precision assembly may be manufactured. Certain PC card, compact flash or small form factor cards are needed that provide a rigid, accurate structure support for applications such as mini disk drives. The current steel covers with plastic molded frames do not provide enough torsional resistance to external forces, for instance, for such precision PC card applications, LCD displays, hinges, security devices, personal digital assistants (PDA), digitization of analog information scanners, internet connections, and other wireless communication applications. Also, traditional molding methods result in too much shrinkage, thus forming surfaces not having accurate dimensions. Therefore, it is desired to provide the manufacture of components such as PC cards using materials and compounds that may provide an accurate datum plane due to accurately manufactured parts which are stiff and strong.
Current packages also include hardware that conveys electricity, such as a wire or printed circuit board (PCB), radiates electromagnetic radiation. The hardware is also susceptible to electromagnetic radiation radiated from other sources. The electromagnetic radiation effects the hardware by corrupting or altering the electrical signal that the component conveys. Such corruption of an electrical signal in a component is not tolerable. The power and associated affect of the electromagnetic radiation field diminishes with distance from the source of the electromagnetic radiation. Therefore, the closely placed electronic components and devices disadvantageously influence each other by radiating electromagnetic fields. Placement of electronic components and devices in close proximity to each other would be acceptable if the effects of the electromagnetic radiation emanating from each device could be muted or lessened to a degree where the electromagnetic radiation emanating from each device does not corrupt the electrical signals being conveyed by other components or devices.
Prior art PCMCIA cards typically have two sheet metal covers which are joined together by a plastic frame molded around each cover, as disclosed in U.S. Pat. No. 5,397,857. U.S. Pat. No. 5,397,857 is hereby incorporated herein by reference. The electrically conductive, sheet metal of the top and bottom covers provide a shielding effect against the transmission of electromagnetic radiation through the top and bottom covers. A seam is formed where the top cover and the bottom cover meet. Due to undulations or unevenness of the sheet metal near the edges of the covers near the seams, some electromagnetic radiation may be able to pass through the region of the seam covered only by plastic material which is, in its natural state, electrically nonconductive, where the plastic material does not provide a shielding effect against electromagnetic radiation, whether the electromagnetic radiation is radiated from components within the PCMCIA card or whether the radiation is radiated from other components external to the PCMCIA card and passes through the seam and into the interior of the PCMCIA card. Such leakage issues are also present in compact flash packages, miniature cards, and other PC card packages, where the term PC card package is inclusive of any package which can contain electrical components, such as the devices described above, and is not to be limited by any narrow definition of the term as used in trade groups.
Other prior art packages employ a clip or veneer of conductive material positioned around the side edges of the package so as to shield against electromagnetic radiation. Another prior art solution, such as U.S. Pat. Nos. 5,505,628 and 5,476,387, employ the use of covers that have mechanical overlaps which attach one cover to the other cover at discrete intervals along the side edge of the package. The mechanical overlaps electrically ground the two covers to each other. The mechanical overlaps traverse or cross over the side edge of the package, as such, only intermittent shielding is provided, which not acceptable. Such solutions, however, add to the size, complexity, material cost, and labor cost of the package.
Thus, there is a need for a simple to manufacture and assemble package that shields the seam of the device package from electromagnetic radiation.
It is an object of the invention to provide a peripheral device package that meets PCMCIA, JEDIC, Compact Flash Association (CFA), and ISO standards. It is a further object of the present invention to provide a package holding a printed circuit board which has a rigid accurate datum on which to build a product on and also reduces the strength of the electromagnetic field emanating from the package and at the same time reduces the influence of electromagnetic radiation, from other sources, on the printed circuit board held within the package.
It is also an object of the present invention to provide a PC card package formed from materials that provide an accurate rigid datum for applications that require precision assemblies.
In one form of the invention the device package takes the form of first and second electrically conductive covers, where each cover has a perimeter. A first electrically conductive frame is attached to the first electrically conductive cover along a portion of the perimeter of the first electrically conductive cover and a second electrically conductive frame is attached to the second electrically conductive cover along a portion of the perimeter of the second electrically conductive cover. The first and second electrically conductive frames are then attached to each other so as to form an electrical connection between the first and second electrically conductive frames. The first and second electrically conductive covers are then secured to each other via the electrically conductive first and second frames. Thus, forming an electrical connection between the first and second electrically conductive covers.
In yet another form of the invention, the invention is a method of assembling the inventive apparatus described above. The inventive method includes the steps of injection molding a first material around a portion of the perimeter of the first electrically conductive cover so as to form the first electrically conductive frame attached to the perimeter of the first electrically conductive cover, where the first electrically conductive cover is electrically connected to the first electrically conductive frame. Likewise, another step includes the injection molding of a second material to form the second electrically conductive frame attached to the second electrically conductive cover in a manner similar to that described in regard to the first electrically conductive cover and frame. Then the two sub-assemblies of an integrated cover and frame are brought together, where the first and second electrically conductive frames are bonded to each other so as to form an electrical connection between each of the parts.
Another embodiment of the method to form a part having a stiff structure thus forming a datum surface. An accurate datum surface is critical to the performance of the component mounted thereto and to the overall performance of the entire package. The method including the steps of placing a metallic material into a molding machine, converting the metallic material to a thixotropic state; transferring the metallic material in the thixotropic state to a mold, where the mold has a portion of an object either fully or partially inserted into the mold; changing state of the metallic material in the thixotropic state to a solid state while being in the mold so as to form the part; and removing the part from the mold, the part having the object bonded thereto.
Thus, Applicants"" invention is superior to the prior art. Applicants"" invention provides a device package that prevents or lessens the strength of an electromagnetic field passing through the seam of the device, as well as preventing or lessening the strength of the electromagnetic field passing through the covers of the device package, while decreasing the part count and providing an easy to assemble package. Therefore, Applicants"" invention achieves the desired objectives. The prior art fails to disclose a PCB carrying package that shields the PCB from electromagnetic radiation both through the cover and the frame of the package where a portion of the frame of the package is exposed to the environment along the seam, which provides the desired result. Such structural features distinguish Applicants"" invention, structurally and functionally, over the prior art of U.S. Pat. No. 5,397,857.